The purposes of this project are to find optimal methods of assessing physical activity energy expenditure (PAEE) in a free-living condition and to use these methods to determine the impacts of physical activity frequency, duration, and intensity on health. We previously collected data, using a variety of accelerometers, heart rate monitors, and pedometers, with which we proposed to estimate PAEE in a cohort of healthy young adults. We simultaneously collected laboratory, nutrition, and anthropometric data from the same cohort. We have worked with the listed collaborators to develop and refine methods to analyze the data collected. We have also used the data derived from this study to develop methods for assessing time spent in sedentary behaviors. We are currently developing protocols in which we will expand the use of several activity monitors to pregnant women with or at risk for diabetes to assess activity patterns and levels of participation in a lifestyle intervention targeting this population. The purpose of this planned application is to clarify the activity patterns, if any, that are most protective of both mother and fetus against the pregnancy complications attributed to obesity and diabetes.